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The porcelain fixture has no grounding mounting points, so I guess it's grounded via that screw that secures the fixture to the box?I was taught a long time ago, during my apprentice days, you do not use TEK screws for electrical connections.

In your case it sounds like the metal box is connected to ground indirectly (although in electricity there is no such thing as indirectly) via the light fixture itself, since it's screwed into the metal box with metal screws. The box itself is connected to EMT so the ground screw is probably not necessary but due to the raintight connector and gaskets etc I wanted to ground the box.

Assessing Underlying Soil: It’s important to assess the soil beneath the tarmac to ensure it can provide sufficient support and stability.